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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 52 |
| 3 | 1212 |
| 4 | 41512 |
| 5 | 1889700 |
| 6 | 107684664 |
| 7 | 7384011796 |
| 8 | 592485333472 |
| 9 | 54488274328836 |
| 10 | 5652345176418280 |
| 11 | 653054114586249684 |
| 12 | 83175314479016845584 |
| 13 | 11578838832843098353732 |
| 14 | 1749242011108507789948312 |
| 15 | 285034599164755404426493140 |
| 16 | 49833544890911336997795542464 |
[1,4,52,1212,41512,1889700,107684664,7384011796, 592485333472,54488274328836,5652345176418280, 653054114586249684,83175314479016845584, 11578838832843098353732,1749242011108507789948312, 285034599164755404426493140, 49833544890911336997795542464] |